A hunter tethers his dog team to his sled using a fan hitch—a type of harness that allows each dog to pick its own way across rough and dangerous terrain. The hunters depend heavily on their Greenland dogs, a hardy breed descended from canines that accompanied immigrants who traveled from Siberia to Greenland some 5,000 years ago. The dogs' thick coats allow them to thrive in temperatures approaching minus 70°F(-56°C). Hunters raise their own packs and train them to pull sleds that weigh upwards of a thousand pounds (450 kilograms).